Preheat the oven to 350 degrees F.
In a large bowl, add flour, sugar, baking soda, salt, cocoa, vanilla, milk, eggs, and butter. Beat with a mixer for 3 minutes.
To the bowl, add blueberries and using a large sturdy spoon, stir them into the mixture.
Line the cupcake pans with paper liners.
Add batter into the cupcake liners (3/4's full).
Bake in a preheated oven until a wooden toothpick comes out clean (for about 20 to 25 minutes). This recipe yields about 55 cupcakes so they need to be baked in batches.
When the cupcake pans are cool enough to handle, transfer the cupcakes to a cooling rack. Let the cupcakes cool before adding the filling and frosting.